title: Gender differences in sagittal standing alignment before pubertal peak growth: the importance of subclassification and implications for spinopelvic loading.
abstract: The aim of this study was to analyze gender differences in sagittal standing alignment at pre-peak height velocity age thereby applying a scientifically sound and practically oriented classification scheme for overall standing balance. The study population consisted of healthy boys (n = 639) and girls (n = 557) before pubertal peak growth. During subjects' habitual standing, sagittal plane measures of the spine, pelvis and lower limbs were collected using a clinical screening protocol. With each subject classified as one of three postural types (neutral, sway-back, or leaning-forward), differences in sagittal plane alignment were analyzed between sexes. The results revealed clear differences between genders in each of the postural types. Within the neutral and sway-back postural subgroups, boys presented more forward inclination of the trunk, more thoracic kyphosis and more pelvis backtilt compared with girls. Within the leaning-forward category, girls displayed more forward trunk lean, less thoracic kyphosis and more pelvic anteversion. A state of lumbar segmental hyperextension appeared to exist in female leaning-forward subjects. Our results reveal for the first time that sagittal standing alignment is different between prepubescent boys and girls when subjects are appropriately subclassified, and conversely represent a 'wash-out effect' when pooled. When the classification system is applied, gender-specificity in gravity line position is suggested, implying gender-related differences in lever arms and thus load. Present findings may add to our understanding of gender-specific biomechanical challenges posed by habitual posture, and may shed new light on sagittal standing alignment as a possible contributory factor in developmental spinal-pelvic disorders.
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Ghent University, Artevelde University College, Ghent, Belgium.
authors.forename: Mieke
authors.initials: M
authors.lastname: Dolphens
authors.forename: Barbara
authors.initials: B
authors.lastname: Cagnie
authors.forename: Andry
authors.initials: A
authors.lastname: Vleeming
authors.forename: Guy
authors.initials: G
authors.lastname: Vanderstraeten
authors.forename: Lieven
authors.initials: L
authors.lastname: Danneels
mesh_terms: D000367:Age Factors; D001696:Biomechanical Phenomena / Q000502:physiology; D002648:Child; D016001:Confidence Intervals; D005260:Female; D006128:Growth; D006801:Humans; D007866:Leg / Q000033:anatomy & histology*; D008297:Male; D010388:Pelvis / Q000033:anatomy & histology*; D004856:Postural Balance / Q000502:physiology; D011187:Posture; D012727:Sex Characteristics; D012737:Sex Factors; D013131:Spine / Q000033:anatomy & histology*
keywords: biomechanics; gender differences; posture types; pubertal peak growth; sagittal balance